Multi layers sound absorbing plate with rigid covering - has foam plastics sound absorbing core and outer casing with holes in it

摘要

A sound absorbing multilayer plate has a sound absorbing core (2, 3) to absorb at least 30% of sound in the 1000-4000 Hz range which is made of a foam plastics material and which is enclosed on all sides by a covering layers (1) to produce a rigid body. At least one of the covering layers allows transmission of the external sound into the sound absorbing core of the plate. This plate has holes cut into its surface to allow sound penetration and these holes occupy at least 5% of the plate surface area. The core material is an open celled foam plastics with a rigidity of at lest 0.2kp/cm3 and may be for example polyurethane foam.